Army helicopters on night maneuvers crashed shortly after takeoff from a helipad in Inje, Gangwon Province, resulting in one death and injury of 21 others, the military said on Monday.

The two UH-60 Black Hawk helicopters collided with each other 15 meters off the ground, injuring 21 soldiers, said sources. A major piloting one helicopter died as a result of injuries sustained in the crash, while 21 others were rushed to two military hospitals.

The military said that while an investigation of the accident is underway, preliminary reports indicated that the main rotor blade of one helicopter struck the tail propeller of the preceding aircraft in the dark. Both machines were badly damaged as they crashed onto the helipad, while debris from the helicoptersdamaged a vehicle in a nearby parking lot.

Of the two downed UH-60s, one held a crew of five, including the pilot and co-pilot. The other was loaded with troops. The two machines were taking part in air assault training involving five helicopters that landed troops before taking off again. The five were part of a larger force of 40 helicopters engaged in military exercises in the city 165 kilometers east of Seoul.

The medium-sized utility and assault helicopters form the backbone of South Korea's helicopter force, replacing the Vietnam-era UH-1s.